Valles had worked for Yahoo first as outside legal counsel, then in-house, since 2008, according to her LinkedIn profile. In 2010, she gave a lecture on privacy and transparency in Monterrey.

Her departure comes at a singularly inopportune time for Yahoo, considering that it's pursuing an appeal of the $2.7 billion judgment that a court awarded Worldwide Directories, Yahoo's former business partner in a telephone-directory project.

Worldwide Directories claimed that it had reached tentative agreements to start extending its telephone-directory partnership beyond Mexico, which led to an award of damages based not just on its Mexican business but the potential business it could have generated around the world.

Yahoo has previously said the original lawsuit is without merit and it has filed an appeal in the case.